1. Field of the Invention
The present invention relates to an ink, an ink-jet recording process using such an ink, a recorded article obtained by such a recording process and instruments using such an ink, and particularly to an ink which can enhance fluorescence intensity and provide a recorded article good in record quality including stability, reliability and coloring ability to look at, an ink-jet recording process using such an ink, a recorded article obtained by the recording process, and instruments using such an ink. The present invention also relates to a method of enhancing fluorescence of a fluorescent colored portion of a recorded article comprising a recording medium and the colored portion provided thereon, and a method of elongating the life time of fluorescence.
2. Related Background Art
Various investigations and reports have heretofore been made on inks for writing utensils and inks for ink-jet. In particular, in order to enhance the quality of recorded articles, including fluorescence intensity and coloring ability, such various proposals as described above have been made. For example, proposals of coloring materials and the like each having a novel structure, which are suitable for use in inks for the above-described use applications, proposals of inks using a coloring material (hereinafter referred to as “fluorescent coloring material”) exhibiting fluorescence properties as a main coloring material, and proposals as to the combined use of a fluorescent coloring material as a coloring material for inks have been made. In particular, the proposals as to inks, which pay attention to the fluorescence properties of fluorescent coloring materials, include Japanese Patent Application Laid-Open Nos. 8-151545, 9-132729, 10-193775, 10-298462 and 10-298467, and Japanese Patent No. 233038, and novel recording processes and fluorescent coloring materials have been proposed therein.
In addition, the proposals as to the use of fluorescent coloring materials include Japanese Patent Application Laid-Open Nos. 5-293976, 6-191143, 6-322307, 7-009755, 7-305013, 8-053639, 9-003375, 9-01294, 9-137097, 9-137098-137099, 9-165539, 9-241565, 9-255904, 9-286939, 10-007962, 10-183043, 11-080639, 11-320921 and 2000-038529, and Japanese Patent No. 2995853.
In recent years, the use applications of fluorescent coloring materials have not been limited to the mere formation of beautiful color images heretofore conducted, and there have been proposed, for example, technical development that fluorescence properties are imparted to an ink, information such as characters, numerals, marks and/or bar codes is recorded on a recording medium with such an ink, and the fluorescent ink is caused to emit light by irradiating the recording medium with ultraviolet light having a proper wavelength, thereby imparting another information (for example, security information) than visible information. Accordingly, there is room to widen the use applications of inks exhibiting fluorescence properties in many fields, and there is a strong demand for development of inks which are stable, reliable, high in fluorescence intensity and excelling in coloring ability.